Year	Years
1970	1.95
1971	2
1972	2.05
1973	2.11
1974	2.16
1975	2.22
1976	2.27
1977	2.33
1978	2.39
1979	2.45
1980	2.51
1981	2.58
1982	2.64
1983	2.71
1984	2.77
1985	2.84
1986	2.91
1987	2.99
1988	3.06
1989	3.13
1990	3.21
1991	3.29
1992	3.37
1993	3.45
1994	3.53
1995	3.62
1996	3.71
1997	3.79
1998	3.88
1999	3.98
2000	4.07
2001	4.16
2002	4.26
2003	4.35
2004	4.45
2005	4.55
2006	4.65
2007	4.76
2008	4.86
2009	4.96
2010	5.07
2011	5.18
2012	5.29
2013	5.4
2014	5.51
2015	5.63